微信小程序支付跟微信公眾號支付類似，這裏不另做記錄，如果沒有開發過支付，可以查看我關於微信支付的文章

重點記錄微信小程序申請退款開發過程中遇到一些坑。

退款接口比支付接口接口多了一個 雙向證書

證書介紹：https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=4_3

由於這裏是Java開發，所有下載apiclient_cert.p12文件，下面是官方給的demo

/*
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   
 
http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <
 
http://www.apache.org/>.
 *
 */
package httpstest;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.security.KeyStore;

import javax.net.ssl.SSLContext;

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
 
import org.apache.http.client.methods.HttpGet;
import org.apache.http.conn.ssl.SSLContexts;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

/**
 * This example demonstrates how to create secure connections with a custom SSL
 * context.
 */
public class ClientCustomSSL {

    public final static void main(String[] args) throws Exception {
        KeyStore keyStore  = KeyStore.getInstance("PKCS12");
        FileInputStream instream = new FileInputStream(new File("D:/10016225.p12"));
        try {
            keyStore.load(instream, "10016225".toCharArray());
        } finally {
            instream.close();
        }

        // Trust own CA and all self-signed certs
        SSLContext sslcontext = SSLContexts.custom()
                .loadKeyMaterial(keyStore, "10016225".toCharArray())
                .build();
        // Allow TLSv1 protocol only
        SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(
                sslcontext,
                new String[] { "TLSv1" },
                null,
                SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
        CloseableHttpClient httpclient = HttpClients.custom()
                .setSSLSocketFactory(sslsf)
                .build();
        try {

            HttpGet httpget = new HttpGet("https://api.mch.weixin.qq.com/secapi/pay/refund");

            System.out.println("executing request" + httpget.getRequestLine());

            CloseableHttpResponse response = httpclient.execute(httpget);
            try {
                HttpEntity entity = response.getEntity();

                System.out.println("----------------------------------------");
                System.out.println(response.getStatusLine());
                if (entity != null) {
                    System.out.println("Response content length: " + entity.getContentLength());
                    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(entity.getContent()));
                    String text;
                    while ((text = bufferedReader.readLine()) != null) {
                        System.out.println(text);
                    }
                   
                }
                EntityUtils.consume(entity);
            } finally {
                response.close();
            }
        } finally {
            httpclient.close();
        }
    }

}

在上面代碼進行微調

private static void ClientCustomSSL(String xmlStr) throws  Exception{
        KeyStore keyStore  = KeyStore.getInstance("PKCS12");
        FileInputStream instream = new FileInputStream(new File("D:/apiclient_cert.p12"));
        try {
            keyStore.load(instream, WxPayConfig.MCH_ID.toCharArray());
        } finally {
            instream.close();
        }

        // Trust own CA and all self-signed certs
        SSLContext sslcontext = SSLContexts.custom()
                .loadKeyMaterial(keyStore, WxPayConfig.MCH_ID.toCharArray())
                .build();
        // Allow TLSv1 protocol only
        SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(
                sslcontext,
                new String[] { "TLSv1" },
                null,
                SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER);
        CloseableHttpClient httpclient = HttpClients.custom()
                .setSSLSocketFactory(sslsf)
                .build();
        try {

            HttpPost httpPost = new HttpPost("https://api.mch.weixin.qq.com/secapi/pay/refund");
            StringEntity entityStr = new StringEntity(xmlStr);
            entityStr.setContentType("text/xml");
            System.out.println("entityStr--------------"+entityStr);
            httpPost.setEntity(entityStr);

            CloseableHttpResponse response = httpclient.execute(httpPost);
            try {
                HttpEntity entity = response.getEntity();

                System.out.println("----------------------------------------");
                System.out.println(response.getStatusLine());
                if (entity != null) {
                    System.out.println("Response content length: " + entity.getContentLength());
                    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(entity.getContent()));
                    String text;
                    while ((text = bufferedReader.readLine()) != null) {
                        System.out.println(text);
                    }

                }
                EntityUtils.consume(entity);
            } finally {
                response.close();
            }
        } finally {
            httpclient.close();
            return null;
        }

    }

參數 String xmlStr 是傳入的封裝好的xml字符串（封裝方法在我微信支付開發的文章裏面有）
然後測試結果

這裏面簽名有個隱藏的坑，就是請求字段，和mic_id都正確，微信簽名驗證也正確，請求就是報簽名錯誤
原因是我的退款原因（refund_desc）參數是中文的，把它調成英文的

不得不說微信支付開發文檔很坑

微信小程序支付開發之申請退款